Omega-3 Fatty Acids: Information for the Veterinary Health Professional

What are omega-3 fatty acids?

Omega-3 fatty acids are polyunsaturated fatty acids (PUFAs) that comprise a small percentage of dietary lipids ingested by humans and animals. The name “omega-3” refers to the location of the double bond closest to the methyl end of the hydrocarbon chain, and may be alternatively referred to as “n-3” in the literature. Chief among the omega-3 fatty acids is alpha-linolenic acid (ALA), which along with linoleic acid (LA, an omega-6 fatty acid), comprise the primary essential fatty acids that must be obtained from the diet (Fig 1). PUFAs and PUFA-containing foods are vulnerable to oxidation and should be eaten promptly or kept under cool conditions and away from oxygen to slow degradation. Antioxidants such as vitamin E can prolong shelf life.

What do PUFAs do?

PUFAs are stored in membrane phospholipids and serve roles in cellular communication and maintenance of membrane fluidity. PUFAs are released from membranes in response to cellular signals and modified into a vast array of communication molecules, many of which have hormone-like properties.

Figuring prominently among these molecules is arachidonic acid (AA), which is an omega-6 fatty acid that most non-carnivorous species make from LA. The downstream products of LA include many of the major inflammatory mediators such as the eicosanoids: prostaglandins, leukotrienes, thromboxanes, and others.

However, the arachidonic acid cascade learned in most medical education is not the whole story of inflammatory mediators. The omega-3 fatty acid eicosopentaenoic acid (EPA) made from the omega-3 ALA provides an alternative substrate for production of several series of eicosanoids with different regulatory profiles than their omega-6 origin counterparts. Substrates of the two fatty acid lineages compete for use of the same enzymes. The products descended from omega-6 precursors tend to be pro-inflammatory (e.g. series 2 prostaglandins and series 4 leukotrienes), while the omega-3 lineage products tend to be less or even anti-inflammatory (e.g. series 3 prostaglandins and series 5 leukotrienes). Generally, eicosanoids made from omega-3 fatty acids dampen inflammation while not adversely affecting the effectiveness of the immune system.

Carnivorous avian species may require pre-formed dietary AA and EPA in addition to LA and ALA, as is known to be the case in mammalian obligate carnivores and fish. For a review of fatty acid chemistry and the role of PUFAs in inflammation, see Calder.

 

What are the health benefits of eating more omega-3 fatty acids?

Because omega-3s modulate the amount and identity of eicosanoids produced, health conditions that involve inflammation such as cardiovascular disease and arthritis may be improved through increased dietary omega-3s. In humans, higher dietary levels of omega-3 have been shown to lower risk of heart attack, stabilize heart function, lower blood pressure and triglyceride levels, and improve blood flow. Studies in guinea pigs and rats have shown a protective effect against arrhythmias. Supplementation of Japanese quail diets with fish oil reduces development of atherosclerosis, and parrots without atherosclerosis have been shown to have higher levels of ALA in tissues than parrots with atherosclerosis.

The ratio of omega-6 to omega-3 in the diet may modulate the inflammatory response more than the overall amount of each. The optimal ratio has not been determined, but lower ratios are considered less inflammatory than high ratios. Western human diets often contain ratios of 10-20:1 or more, and most commercial parrot diets have ratios in the range of 15-25:1. Most Lafeber avian diets are formulated to offer ratios of 10:1 (Klasing KC, pers. comm. Sept 24, 2009). Lafeber’s critical care diets at LafeberVet provide even lower ratios for nutritional support during illness; for example, Emeraid Carnivore provides a ratio of 8:1 (Duerr RS, unpublished data April 8, 2009).

 

What are dietary sources of omega-3 fatty acids?

Alpha-linolenic acid is found in many plant foods including algae, leafy green vegetables, broccoli, strawberries, nuts such as walnuts, and oils like canola, soy, and flax (Fig 2). Animal sources include oily fish, such as herring, mackerel or sardines, plus meat or eggs from animals that eat grasses and insects. Many Lafeber products contain canola oil or rapeseed as a source of omega-3 fatty acids.

 

How much omega-3 fatty acid do psittacines need?

Optimal levels of omega-3 fatty acids for Psittacines are unknown. Experimental data from poultry studies typically evaluate the effects of omega-3 supplementation on growth and reproduction rather than optimizing maintenance of good health in adult birds. Linoleic acid fed at 1% of the diet appears adequate for growth and reproduction in domestic galliformes. Extrapolating from this at 10:1 would result in omega-3s comprising at least 0.1% of the diet.

It is preferable to replace existing fat in the diet with omega-3s rather than adding additional fat. Adverse effects of omega-3 supplementation appear limited to those of excessive fat consumption, such as obesity and diarrhea; however, omega-3 fatty acids usually result in less fat deposition than an equal amount of omega-6 or saturated fatty acids.

Omega-3s are being used as therapeutics for avian medical problems that would logically benefit from improved cardiovascular dynamics or reduced inflammatory responses, such as feather picking and renal disease. Further research into the health benefits of omega-3 fatty acids for parrots is needed.

 

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